The author has the source code for the Caddy modules referenced as
github.com/[username]/[module]. I opted instead to nest the modules within the
chapter directory. In order for the modules to be used within main.go, I have
used the following terminal commands to add local references within go.mod.
go mod edit -replace github.com/nicholas-fedor/Network-Programming-with-Go/Ch10/caddy-restrict-prefix=./caddy-restrict-prefix
go mod edit -replace github.com/nicholas-fedor/Network-Programming-with-Go/Ch10/caddy-toml-adapter=./caddy-toml-adapter